This invention relates to a method of forming oxide superconducting films of Y-Ba-Cu-O (Y is at least one element selected from among Y and Ln (lanthanoids); and other systems while enabling the film to be suitably oriented (e.g., the c-axis is parallel to the substrate). The invention also relates to oxide superconducting members having the oxide superconducting films formed by that method. The concept of this invention is applicable to the fabrication of devices such as Josephson junctions.
A method has been known that produces an oxide superconductor by applying a laser beam onto a film formed by coating a solution containing organic metal salts (see Unexamined Published Japanese Patent Application No. 255506/1990). In this method, ultraviolet rays are applied as an auxiliary source of exciting light. A method is also known whereby a thin film is formed containing a Y-Ba-Cu-O system, with the c-axis being parallel to a substrate such as MgO. This method utilizes sputtering in an O.sub.2 -Ar atmosphere under vacuum (see Science, Vol. 249, 28 Sep. 1990 Reports, 1549- 1552; Appl. Phys. Lett, 57(23), 3 Dec. 1990 p. 2484-2486; and Physica C 170(1990), 325-332, North Holland).
Many versions of the MOCVD process (organic metal chemical vapor deposition process) have been known as techniques for forming oxide films or oxide superconducting films by application of ultraviolet or laser light. See, for example, Proceedings of the 37th Symposium of the Japan Society of Applied Physics, spring 1990, p. 136, 27a-PB-7, 27a-PB-9 and page 138, 27a-PB-15; Proceedings of the 2nd International Symposium on Superconductivity (ISS '89), Tsukuba, 1989, p. 767; Unexamined Published Japanese Patent Application Nos. 230522/1988, 224117/1988, 225599/1988 and 224116/1988.
However, the prior known method proposed in Unexamined Published Japanese Patent Application No. 255506/1990 does not rely upon CVD and, as shown in FIG. 14, the c-axis of the oxide film formed by this method is not oriented in a constant direction as being parallel to the substrate but the ab-plane is parallel to the temperature gradient.
The second method which forms a superconducting film having the crystal growth direction oriented along the a-axis also does not rely upon CVD and, furthermore, the desired thin film oriented along the a-axis cannot be readily formed at a desired location in the matrix.
In addition, the many versions of the MOCVD process are not such that an oxide superconducting film oriented along the a-axis can be formed in a desired location.